1. Field of the Invention
The present invention concerns 2,4,6-trimethyl-4-phenyl-1,3-dioxane of the general Formula C. ##STR2##
2. Description of the Related Art
In the fragrance industry, there is a constant need for new aromatic substances. The employment of 2,4,6-trimethyl-4-phenyl-1,3-dioxane of the general Formula C in fragrance mixtures is already known and is referenced in patent documents WO 9629281 (The Procter & Gamble Company, USA), JP 62205200 (Kao Corp., Japan), and JP 60014859 (Ogawa and Co., Ltd., Japan). Information regarding the isomer forms of the 1,3-dioxane C, or as the case may be, the specific sensory characteristics, are not to be found in these documents.
In the Chemical Abstracts (Chem. Abs. Vol. 64, 11217f [1966]), there is reference to a patent of the Sanyo Chemical Industry Co. (of K. Uno et al., Japan. 102 ('66), January 7, Appl. Nov. 28, 1962) which concerns the production of 1,3-dioxanes from aliphatic aldehydes with olefins under alumina catalysis. As an example, the conversion of two molar equivalents of paraldehyde (corresponding to six mole equivalents of acetaldehyde) to 2,4,4,6-tetramethyl-1,3-dioxane is carried out with three mole equivalents isobutene in the presence of acidic alumina. It is indicated that in a similar manner 2,4,6-trimethyl-4-phenyl-3-dioxane of general Formula C can be produced, which to the person of ordinary skill in this art means that the 1,3-dioxane of general Formula C was synthesized from the corresponding amounts of .alpha.-methylstyrol (A) and paraldehyde (B) in the presence of acidic alumina. ##STR3##
R. El Gharbi et al. (Synthesis 1971, 361-2; Tetrahedron Vol. 39, 2953-63 [1983]) describe mixtures of two isomeric forms (diasteriomeric enantiomer pairs 1 and 2) of 2,4,6-trimethyl-4-phenyl-1,3-dioxane. The isomers (2RS,4SR,6RS)-2,4,6-trimethyl-4-phenyl-1,3-dioxane (1) and (2RS,4RS,6RS)-2,4,6-trimethyl-4-phenyl-1,3-dioxane (2) are formed in easily distinguishable relationship by condensation of alpha-methylstyrol (A) with two mole equivalents of acetaldehyde under catalysis of strongly acidic cationic exchange resins (Lewatit.RTM. SP 120, Bayer AG) depending upon solvents and reaction time and temperature. For the conversion in toluol at 20.degree. C., there is reported after twenty-four hours a relationship of 1/2 of 68:32; for the conversion in hexane at 20.degree. C. after one hour, or as the case may be at 50.degree. C. after 0.5 hours, there is reported a relationship 1/2 of 62:38, or as the case may be, 65:35. The person of skill in this art would easily conclude therefrom that under the above-described reaction conditions the thermodynamic equilibrium, for example, during the conversion in toluol after 24 hours, was achieved with the 68:32 relationship of substances 1 and 2.
R. el Gharbi et al. observed that the condensation of an alkene with aliphatic and aromatic aldehydes--with the exception of formaldehydes--in the presence of sulfuric acids generally leads to a complex product mixture (glycols, dimers, crotonization of the aldehydes, polymers, etc.), so that this catalyst appears to be unsuitable for achievement of good yields of the corresponding substituted 1,3-dioxanes.
Information or data regarding the sensory properties of 1 and 2, or as the case may be the mixtures thereof, are not included in the two above-described publications. ##STR4##
A mixture of isomers 2,4,6-trimethyl-4-phenyl-1,3-dioxanes, which contains as main components the isomers 1 and 2, has been employed for more than twenty years as an aromatic substance and sold under the names VERTACETAL (manufacturer: Dragoco Gerberding & Co. AG, Holzminden) and FLOROPAL/CORPS 717 (manufacturer: Haarmann & Reimer GmbH, Holzminden).
The two commercial products differ--as has now been determined by in-house analysis--with respect to their content in the main components 1 and 2, but differences have now also been determined with respect to the content of the now identified, respectively present minor constituents (2RS,4SR,6SR)-2,4,6-trimethyl-4-phenyl-1,3-dioxane (3) and (2SR,4SR,6RS)-2,4,6-trimethyl-4-phenyl-1,3-dioxane (4) as well as the minor components 3,6-dihydro-cis-2,6-dimethyl-4-phenyl-2H-pyran (5) and 3,6-dihydro-trans-2,6-dimethyl-4-phenyl-2H-pyran (6) (compare this to the below "comparative analysis"). The compounds 3, 4, and 6 were previously not known, they are described in greater detail below and spectroscopically analyzed in the context of the Examples. ##STR5##
In the corresponding product specification sheets, the aroma of VERTACETAL is described as "fresh-herbal, typically the impression of grapefruit", and the aroma of FLOROPAL/CORPS 717 is described as "herbal-fresh, floral-green similar to chrysanthemum, cyprus, and grapefruit." A respective individualized sensory description of the two main components 1 and 2 as well as the minor components 3, 4, 5, and 6 has not previously been available.